std::unordered_set::insert

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Containers library

array (C++11)

vector

deque

forward_list (C++11)

list

set

multiset

map

multimap

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

stack

queue

priority_queue

 

std::unordered_set

Member functions

unordered_set::unordered_set

unordered_set::~unordered_set

unordered_set::operator=

unordered_set::get_allocator

Iterators

unordered_set::beginunordered_set::cbegin

unordered_set::endunordered_set::cend

Capacity

unordered_set::erase

unordered_set::size

unordered_set::max_size

Modifiers

unordered_set::clear

unordered_set::insert

unordered_set::emplace

unordered_set::emplace_hint

unordered_set::erase

unordered_set::swap

Lookup

unordered_set::count

unordered_set::find

unordered_set::equal_range

Bucket interface

unordered_set::begin(int)

unordered_set::begin(int)

unordered_set::bucket_count

unordered_set::max_bucket_count

unordered_set::bucket_size

unordered_set::bucket

Hash policy

unordered_set::load_factor

unordered_set::max_load_factor

unordered_set::rehash

unordered_set::reserve

Observers

unordered_set::hash_function

unordered_set::key_eq

 

std::pair<iterator,bool> insert( const value_type& value );	(1)	(since C++11)
std::pair<iterator,bool> insert( value_type&& value );	(2)	(since C++11)
iterator insert( const_iterator hint, const value_type& value );	(3)	(since C++11)
iterator insert( const_iterator hint, value_type&& value );	(4)	(since C++11)
template< class InputIt > void insert( InputIt first, InputIt last );	(5)	(since C++11)
void insert( std::initializer_list<value_type> ilist );	(6)	(since C++11)

Inserts element(s) into the container, if the container doesn't already contain an element with an equivalent key.

1-2) Inserts value.

3-4) Inserts value, using hint as a non-binding suggestion to where the search should start.

5) Inserts elements from range [first, last).

6) Inserts elements from initializer list ilist.

If rehashing occurs due to the insertion, all iterators are invalidated. Otherwise iterators are not affected. References are not invalidated. Rehashing occurs only if the new number of elements is greater than max_load_factor()*bucket_count().

Parameters

hint	-	iterator, used as a suggestion as to where to insert the content
value	-	element value to insert
first, last	-	range of elements to insert
ilist	-	initializer list to insert the values from
Type requirements
- InputIt must meet the requirements of InputIterator.

Return value

1-2) Returns a pair consisting of an iterator to the inserted element (or to the element that prevented the insertion) and a bool denoting whether the insertion took place.

3-4) Returns an iterator to the inserted element, or to the element that prevented the insertion.

5-6) (none)

Exceptions

1-4) If an exception is thrown by any operation, the insertion has no effect.

Complexity

1-4) Average case: O(1), worst case O(size())

5-6) Average case: O(N), where N is the number of elements to insert. Worse case: O(N*size()+N)

Notes

The hinted insert (3,4) does not return a boolean in order to be signature-compatible with positional insert on sequential containers, such as std::vector::insert. This makes it possible to create generic inserters such as std::inserter. One way to check success of a hinted insert is to compare size() before and after.

See also

emplace	constructs element in-place (public member function)
emplace_hint	constructs elements in-place using a hint (public member function)